It's too early to break out the Champagne, but you might want to start icing down the bottle. U.S. carbon emissions from electricity-generating power plants dropped 3.8 percent in 2012, to their lowest level since 1994, according to the federal government's Energy Information Administration (EIA). The United States hasn't won the fight to reduce carbon emissions yet, but it's headed in the right direction.

That recent reduction is not an anomaly: energy-related carbon emissions have declined in five of the last seven years, for a 12 percent reduction between 2005 and 2012.

The U.S. decline appears to be part of a long-term trend due primarily to power plants increasingly switching from coal to cheap and cleaner-burning natural gas -- which emits about half the CO2 that coal does -- and to a shift from a manufacturing economy to a service economy, which needs less energy to produce its products.

In addition, the Environmental Protection Agency (EPA) keeps pushing regulations that make it increasingly difficult and costly to use coal.

And that reduction trend may accelerate. While power plants are the primary source of carbon emissions, vehicles also play a role. The widespread availability of cheaper and cleaner natural gas also explains why there is a growing effort to shift long-haul trucks to natural gas instead of diesel fuel.

Engine manufacturer Cummins has begun building and shipping big-rig engines that run on natural gas. And United Parcel Service (UPS) intends to expand its fleet of 18-wheelers that run on liquefied natural gas (LNG) by nearly 800 percent by the end of 2014, according to the New York Times.

Transportation consultant Karl Ziebarth thinks the trucking industry will have largely shifted to natural gas within five to eight years. He notes another reason for the shift is being driven by EPA regulations that require new pollution-control technology that's driving up the price of diesel engines. Challenges remain, including the need for a refueling infrastructure, but he says the growing demand will likely induce truck stop operators to make the needed investment.

Cars are also following suit, though the numbers are small. The Washington Post cites Dave Hurst of Pike Research estimating that out of 14.5 million passenger cars and trucks sold in the U.S. in 2012, a little more than 20,000 ran on natural gas. But even more than long-haul trucks, people will need a convenient refueling infrastructure before natural gas-powered cars catch on.

And even trains may be headed down the same track. BNSF Railway announced earlier this year that it is working on a new engine that will run on LNG -- ironically, to transport what it hopes will be a million barrels of oil a day, according to CNBC.

But even as the U.S. makes progress in reducing carbon emissions, global CO2 emissions between 2005 and 2011 increased by 15 percent. The best way to make sure the rest of the world continues reducing carbon emissions is to remove a decades-old restriction on exporting natural gas to other countries without approval from the federal government.

Not everyone is happy about the U.S. CO2 reduction success story, however. Some environmentalists see the increased availability and adoption of natural gas as a failure because it relaxes the economic pressure on government to mandate individuals and companies switch to renewable energy such as wind and solar power.

Nothing creates more public support for renewable energy sources than high fossil fuel prices. Of course, nothing is worse for the economy than high fossil fuel prices, too.

The day may come when we can get most or all of the energy we need from renewable sources, but that day is a long way off even under the best of circumstances.

The public policy goal should be to meet out energy needs while doing as little damage as possible to the environment and the economy. Natural gas is helping us do that. With the right policies coming out of Washington and the states, we could start celebrating the CO2 reduction success story soon.

Merrill Matthews is a resident scholar with the Institute for Policy Innovation in Dallas, Texas.